The Buckshot Racing #77 custom main jet kit is a precision-engineered set of replacement jets compatible with Mercury outboard carburetors, designed for serious marine engine tuners who require accuracy, durability, and clarity in part identification.
 
This kit includes two (2) of each jet size, providing a comprehensive solution for fine-tuning fuel delivery in Mercury WH, WMH, and WMV carburetor models. Each jet is custom laser-marked for easy identification, even after extended use and exposure to fuel and oil residues.
 
This kit covers five essential jet sizes—80, 82, 84, 86, and 88—which correspond directly with the following OEM part numbers from Mercury:
 
Jet Size 0.080 Inch – Mercury OEM Part Number 1395-6201
Jet Size 0.082 Inch – Mercury OEM Part Number 1399-3518
Jet Size 0.084 Inch – Mercury OEM Part Number 1399-3517
Jet Size 0.086 Inch – Mercury OEM Part Number 1395-5815
Jet Size 0.088 Inch – Mercury OEM Part Number 1395-6202
 
These jets are fully compatible with a wide range of Mercury 2-stroke outboards, including the 2.0L, 2.4L, 2.5L, and 3.0L platforms.
 
Whether you're running a Mercury 135 HP, 150 HP, 175 HP, 200 HP, 225 HP, 250 HP, or a performance variant like the XR2, XR4, XR6, XB, Pro XS, SST-120, SST-140, or the classic Black Max series, this kit allows for proper tuning of the fuel system to match performance demands and environmental conditions.
 
Mercury main jets play a critical role in regulating fuel delivery from the carburetor to the engine’s combustion chamber. In WH-series carburetors, they are a fundamental part of the idle circuit, which affects low-RPM operation and smooth idling. In WMH and WMV carburetors, these jets regulate fuel in the main fuel circuit, which governs mid-to-high throttle behavior.
 
Selecting the correct jet size allows for a precisely tuned fuel-to-air ratio, which is crucial for achieving the following:
 
Engine performance is directly affected by jet sizing. Too small a jet can lead to a lean condition—risking detonation or overheating—while too large a jet can result in a rich mixture that fouls plugs, reduces power, and wastes fuel. The Buckshot Racing #77 kit allows for careful tuning to match environmental factors such as altitude, temperature, humidity, and the effects of engine modifications like porting, compression increases, or aftermarket reeds and exhaust systems.
 
Each main jet in the Buckshot Racing kit is laser-marked with its size, ensuring quick and accurate identification even during field maintenance or race-day tuning. This added precision and durability are especially important in high-stakes marine racing or performance boating applications, where quick and confident adjustments are often necessary.
 
By covering the most commonly used Mercury OEM main jet part numbers—1395-6201, 1399-3518, 1399-3517, 1395-5815, and 1395-6202—this kit gives engine builders and tuners the flexibility to optimize combustion for peak power output, enhanced engine reliability, and improved fuel economy.
 
Whether you are rebuilding a classic WH-style carburetor or fine-tuning a WMH or WMV-equipped 2-stroke outboard, the Buckshot Racing #77 jet kit provides the accurate, race-proven components needed for consistent engine performance in all conditions.
 
Includes ten (10) main jets: 2 x 80s, 2 x 82s, 2 x 84s, 2 x 86s, 2 x 88s. 
 
Tuning Notes:
 
In high-performance applications, it is possible to stagger main jet sizes across the carburetors to account for how heat distributes throughout the engine—especially during extended wide-open throttle (WOT) operation.
 
As the engine runs at full power, the lower cylinders (typically cylinders 5 and 6) tend to build heat by the exhaust exit and run hotter compared to the middle ones (3 and 4) and the top cylinders (1 and 2). This heat buildup can lead to a leaner air-fuel mixture in lower cylinders if the jets are all the same size.
 
To compensate for this, slightly larger main jets are installed in the bottom two carburetors that feed cylinders 5 and 6,  and also 3 and 4.
 
This enriches the fuel mixture for those cylinders, helping to keep temperatures under control and prevent potential engine damage like detonation or piston scuffing. The middle and upper carburetors use slightly smaller jets, tuned to match their thermal and airflow characteristics.
 
This technique ensures a more balanced fuel delivery across all cylinders, which can improve reliability and overall engine performance under high-load conditions.
 
For more information, contact Mike Hill at 714-697-1716 or email mike@buckshotracing77.com